Styrene Monomer CAS 100-42-5
Chelora Chemicals supplies inhibitor-stabilised styrene monomer to polystyrene, ABS, SBR latex and unsaturated polyester producers worldwide. Because styrene polymerises on warm storage, every consignment leaves with a batch-specific COA including TBC, polymer and aldehyde data, the current SDS and full dangerous-goods documentation.
Also known as: SM · Vinylbenzene · Phenylethylene · Ethenylbenzene · Styrol
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Price, lead time and a sample COA for Styrene Monomer, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (GC purity, TBC, polymer, aldehydes)
- Safety Data Sheet (SDS)
- Transport and dangerous-goods documents
- Third-party inspection on request
- Certificate of origin
What is Styrene Monomer?
Styrene monomer is a vinyl aromatic, formula C₈H₈, a benzene ring carrying a reactive vinyl group. It is a clear, flammable liquid boiling at 145 °C with a sharp sweet odour that becomes unpleasant at higher concentration.
The vinyl group polymerises readily, by free radical, anionic or coordination routes, which makes styrene one of the most versatile monomers in the industry. It homopolymerises to polystyrene and copolymerises with butadiene, acrylonitrile and unsaturated polyester resins.
That same reactivity is the handling problem. Styrene self-polymerises on warm storage, exothermically, so it is always shipped with TBC inhibitor and kept cool. An uninhibited warm tank is a genuine runaway risk rather than a quality concern.
Why Styrene Monomer specifically
- A reactive vinyl group. Polymerises by multiple mechanisms, giving process flexibility across the plastics and rubber industries.
- The aromatic ring. Gives polystyrene its rigidity, clarity and electrical properties.
- A universal comonomer. Copolymerises with butadiene for SBR, with acrylonitrile for SAN and ABS, and crosslinks unsaturated polyester.
- Inhibitor dependent. TBC and dissolved oxygen together keep the monomer stable; both have to be managed.
How Styrene Monomer is Manufactured
Styrene is made by dehydrogenating ethylbenzene, or as a co-product of propylene oxide manufacture.
- Ethylbenzene feed. Benzene alkylated with ethylene over zeolite catalyst supplies the feedstock.
- Catalytic dehydrogenation. Ethylbenzene and superheated steam pass over a potassium-promoted iron oxide catalyst at about 600 °C under vacuum.
- Quench and separation. The reactor effluent is quenched and the hydrocarbon phase separated from condensed steam.
- Vacuum distillation. Styrene is distilled under vacuum at low temperature to avoid polymerisation, with inhibitor dosed in the columns.
- PO/SM co-production. The alternative route oxidises ethylbenzene to the hydroperoxide, epoxidises propylene, then dehydrates the alcohol to styrene.
- Final inhibition. TBC at 10 to 15 ppm is added to the finished monomer, with dissolved oxygen maintained for the inhibitor to work.
Typical Commercial Specification
Figures below are representative of commercial styrene monomer. Tell us your polymerisation route and we will advise on the aldehyde and peroxide limits you should specify.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless liquid, free of suspended matter |
| Styrene purity | 99.8% min by weight |
| Inhibitor (TBC) | 10 – 15 ppm, to customer requirement |
| Polymer content | To grade, typically 10 ppm max |
| Aldehydes (as benzaldehyde) | To grade, typically 50 ppm max |
| Peroxides (as H₂O₂) | To grade, typically 20 ppm max |
| Ethylbenzene | To grade, typically 500 ppm max |
| Chlorides | To grade, typically 1 ppm max |
| Water | To grade, typically 200 ppm max |
| Colour (Pt-Co) | 10 max |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₈H₈ (C₆H₅CH=CH₂) |
| Molecular weight | 104.15 g/mol |
| Appearance | Clear colourless liquid, sharp sweet odour |
| Boiling point | 145 °C |
| Melting point | −30.6 °C |
| Flash point | About 31 °C (closed cup) |
| Density | 0.906 g/cm³ at 20 °C |
| Vapour pressure | About 0.6 kPa at 20 °C |
| Vapour density (relative to air) | 3.6, heavier than air |
| Flammable limits in air | About 1.1 to 6.1% by volume |
| Autoignition temperature | About 490 °C |
| Polymerisation heat | About 670 kJ/kg — substantial exotherm |
| Solubility in water | Low (about 0.3 g/L at 20 °C) |
| Incompatibilities | Oxidisers, peroxides, acids, aluminium chloride, copper |
Behaviour in the process
Styrene's reactivity defines almost every handling rule that applies to it:
- Self-polymerisation. Rate roughly doubles with every 10 °C rise. Above about 65 °C the exotherm can become self-sustaining.
- Inhibitor needs oxygen. TBC only functions with dissolved oxygen present, so a full nitrogen blanket is wrong for styrene; air headspace or controlled oxygen is standard.
- Popcorn polymer. Insoluble polymer seeds can grow in vapour spaces and dead legs, especially where rust is present.
- Peroxide formation. Aged or air-saturated material forms peroxides that initiate polymerisation.
Styrene Grades and Related Monomers
Styrene is sold to a single specification with the inhibitor level adjusted to the customer's storage time and temperature.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| Standard styrene monomer | 99.8%+, 10–15 ppm TBC | Polystyrene, ABS, SAN, SBR and latex production |
| Low-inhibitor styrene | Reduced TBC for immediate use | Short supply chains and anionic polymerisation |
| High-inhibitor styrene | 50 ppm or more TBC | Long sea voyages and extended storage |
| Alpha-methylstyrene | C₉ vinyl aromatic, CAS 98-83-9 | Heat-resistant ABS and resin modification |
| Methyl methacrylate | Acrylic monomer, CAS 80-62-6 | Different polymer family; a comonomer rather than a substitute |
Stated plainly: nothing substitutes for styrene in polystyrene or ABS. The real variable is the inhibitor level, which should be matched to the time and temperature the monomer will see before it is consumed.
Industries We Supply Styrene Monomer To
The same stabilised monomer goes to a polystyrene reactor, a latex plant and a composites resin house. What changes is the inhibitor level and the aldehyde ceiling.
Where Styrene Monomer is Used
Polystyrene and EPS take the largest share of styrene, with ABS, SBR latex and unsaturated polyester resins behind them.
In polystyrene manufacture
Styrene is polymerised in bulk or suspension by free radical initiation, with the chain length controlled by temperature and initiator. Aldehyde content matters because benzaldehyde and similar carbonyls act as chain transfer agents, shifting molecular weight. The inhibitor is consumed in the first stage rather than removed.
In unsaturated polyester resins
Styrene is both a solvent for the polyester and the crosslinker that cures it. The styrene content sets viscosity, cure speed and the final mechanical properties, and styrene emissions during open moulding are the main regulatory pressure point on this application.
Need a specific grade, purity and packing format?
Tell us the grade, your inhibitor requirement and the aldehyde limit your polymerisation needs, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with inhibitor and polymer figures reported alongside purity because they are safety-critical for this monomer.
- Styrene purity — by gas chromatography, the primary grade measure.
- TBC inhibitor level — by colorimetry, confirming the stability margin for your storage time.
- Polymer content — reported because it indicates whether polymerisation has already begun.
- Aldehydes — measured because carbonyls act as chain transfer agents.
- Peroxides — tested because they initiate uncontrolled polymerisation.
- Chlorides, water and colour — confirming freedom from contamination and corrosion risk.
Common Process Problems & Likely Causes
When styrene causes trouble, it is usually inhibitor depletion, temperature, aldehydes or rust. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Polymer or gel in the tank | Inhibitor depleted, warm storage or rust seeding | TBC level, tank temperature history and internal condition |
| Tank temperature rising without heating | Self-polymerisation exotherm starting | Immediate cooling, inhibitor top-up and emergency procedure |
| Molecular weight off target | Aldehydes acting as chain transfer agents | Aldehyde figure on the COA |
| Slow or incomplete cure in UPR | Residual inhibitor higher than the formulation allows | TBC level against your initiator package |
| Yellow colour in the polymer | Oxidation products or peroxides in the monomer | Colour and peroxide results |
| Popcorn polymer in dead legs | Stagnant monomer in vapour space with rust present | Line flushing, tank cleanliness and inspection schedule |
Packaging, Storage & Shipping
- Standard packing. 200 L drums, IBCs, ISO tank containers, road tankers and bulk parcel cargoes.
- Temperature control. Store below 25 °C, ideally below 20 °C. Polymerisation rate roughly doubles for each 10 °C rise.
- Oxygen, not nitrogen. TBC requires dissolved oxygen to function. Air headspace or controlled oxygen is standard; a full nitrogen blanket disables the inhibitor.
- Storage. Shaded, earthed and bunded flammable-liquid tankage with temperature monitoring and high-temperature alarms.
- Material compatibility. Carbon steel or stainless steel. Avoid copper and rust, which seed popcorn polymer.
- Stock rotation. First in, first out. Inhibitor depletes over time and shelf life is finite.
- Shelf life. Typically three months at 25 °C, longer if cooler. Re-test TBC and polymer content on aged stock.
- Transport classification. UN 2055, styrene monomer stabilised, Class 3 flammable liquid, packing group III.
Hazards & Safe Handling
Styrene is a flammable liquid, a reproductive and respiratory hazard, and a self-reactive monomer. The polymerisation exotherm is the most serious process-safety issue associated with it.
- Polymerisation runaway. Self-polymerisation is exothermic and accelerates with temperature. Maintain inhibitor, control temperature and provide emergency cooling and relief.
- Flammability. Flash point about 31 °C with a flammable range of roughly 1.1 to 6.1%. Control ignition sources and bond transfer equipment.
- Health classification. Suspected of damaging the unborn child, causes organ damage through prolonged exposure, and classified by IARC as probably carcinogenic to humans.
- Occupational exposure. Limits commonly sit between 10 and 20 ppm as an 8-hour average; confirm the limit in your jurisdiction.
- Odour and irritation. Strongly irritating to eyes and respiratory tract; the odour threshold is well below the exposure limit.
- PPE. Chemical-resistant gloves, eye protection, flame-resistant clothing and respiratory protection for any breach of containment.
- Environment. Harmful to aquatic life; prevent entry to drains and watercourses.
Regulatory & Compliance Notes
Styrene is a regulated monomer with transport, occupational and emissions controls. The notes below are orientation rather than legal advice.
- GHS classification. Flammable liquid Category 3, reproductive toxicity Category 2, STOT RE Category 1, skin and eye irritant.
- Carcinogenicity listings. Classified by IARC as probably carcinogenic to humans and listed as reasonably anticipated to be a human carcinogen in the US.
- Dangerous goods transport. UN 2055, styrene monomer stabilised, Class 3, PG III. Stabilisation is a transport requirement, not an option.
- Emissions regulation. Open-mould composite operations face styrene emission limits in most jurisdictions.
- REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
- Quality agreements. Polymer producers commonly expect documented TBC, polymer and aldehyde limits with change control.
We Supply Styrene Monomer Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Styrene Monomer from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
- Flexible volumes. From a pallet of drums up to repeat bulk shipments on a supply contract.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Styrene Monomer from Chelora
We are an independent sourcing and supply partner. For styrene that means settling three things at enquiry: the inhibitor level matched to your transit and storage time, the aldehyde and peroxide limits your polymerisation tolerates, and the temperature-controlled route into your tankage.
- Documentation on every lot. Batch-specific COA (GC purity, TBC, polymer, aldehydes), plus SDS and the full transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. From a pallet of drums through to full bulk shipments on contract supply.
- Grade matching. Standard, low-inhibitor or high-inhibitor styrene matched to your transit time, storage temperature and polymerisation route.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. 1,3-Butadiene, Acrylonitrile, Ethylbenzene and other feedstocks alongside Styrene Monomer from one supplier.
How ordering works
- Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
- We quote. Price, lead time, packing format and a sample COA, normally within one working day.
- Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.
Styrene Monomer — Common Questions
The questions our technical desk is asked most often about Styrene Monomer. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of styrene monomer?
The CAS number for styrene is 100-42-5, and its EC number is 202-851-5. Its molecular formula is C₈H₈ with a molecular weight of 104.15 g/mol, and it is classified under HS code 2902.50.
What is styrene used for?
For polystyrene and expandable polystyrene, ABS and SAN copolymers, styrene-butadiene rubber and latex, unsaturated polyester resins, SBS and SIS block copolymers, and ion exchange resins.
Do you supply styrene monomer worldwide?
Yes. Chelora Chemicals supplies and exports styrene monomer worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India. Every consignment carries the COA with inhibitor and polymer data, the SDS and the dangerous-goods documentation.
Why does styrene need an inhibitor?
Because it self-polymerises exothermically on warm storage. TBC at 10 to 15 ppm scavenges the radicals that start the chain reaction. Without it, a warm tank can heat itself to a runaway.
Why must styrene have oxygen present, unlike butadiene?
TBC only functions as an inhibitor when dissolved oxygen is available to it. A full nitrogen blanket disables the inhibitor, which is why styrene is stored with air headspace or controlled oxygen rather than fully blanketed.
How is styrene manufactured?
Mainly by catalytic dehydrogenation of ethylbenzene over promoted iron oxide at about 600 °C with steam dilution. The other route co-produces styrene with propylene oxide through the ethylbenzene hydroperoxide process.
Is styrene hazardous?
Yes. It is a flammable liquid, suspected of damaging the unborn child, causes organ damage through prolonged exposure, and is classified by IARC as probably carcinogenic. The polymerisation exotherm is a serious process-safety hazard in its own right.
What are the UN number and transport class?
UN 2055, styrene monomer stabilised, Class 3 flammable liquid, packing group III. Stabilisation is required for carriage, not optional.
How should styrene be stored?
Below 25 °C in shaded, earthed and bunded tankage with temperature monitoring and alarms, with air headspace or controlled oxygen so the inhibitor works, away from rust and copper.
What is the typical shelf life?
Around three months at 25 °C and longer at lower temperatures, limited by inhibitor consumption. Re-test TBC and polymer content rather than assume.
What packing sizes and order quantities are available?
200 L drums, IBCs, ISO tank containers, road tankers and bulk parcels. Orders run from a pallet of drums up to repeat bulk cargoes on contract supply.
Can I buy styrene with more or less inhibitor?
Yes, and you should specify it. Long sea voyages and warm climates call for higher TBC, while short supply chains and some polymerisation routes prefer a lower level so less inhibitor has to be overcome at the reactor.
Ready to source Styrene Monomer?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.